Table 1: Features of various ultrasonic evaluation methods.

MethodKey to Figure 1TransducerPositivesComments

Through transmission(a)T + RSimpler electronics compared to (c)Continuous wave and pulse operation are possible
Pitch-catch(b)T + RSingle side access required only compared to (a)Same as (a)
Pulse-echo(c)T/RSingle transducer required only compared to (a, b)Pulse operation only
Backscatter(d)T/RNo reflector required compared to (c)Same as (c); effective for highly scattered media
Acoustic emission(e)RNo need for transmitter and its driverSignals are difficult to interpret; limited applicability